1. Field of the Invention
The present invention relates to a microphone apparatus, and more particularly to an acoustic structure, which is applied to a radio apparatus, a recording apparatus and the like in which a microphone is built in a microphone case or a main housing, for resolving the problem in which clarity of voice information to be absorbed is lost by a phenomenon in which transmitting voice with a strong sound pressure or under strong wind, wind noise or prosodic features of voices based on various kinds of languages and individual differences are generated.
2. Description of the Related Art
Conventionally, in a mobile-use radio apparatus, a microphone is built in a microphone case, which is cable-connected to a main body. In a handy-type transceiver, a microphone is built in a housing.
In accordance with miniaturization and supersensitization of the microphone, there has been recently adopted a system wherein a small sound absorbing hole is formed on a microphone case or a housing panel and the microphone is held on the back thereof and a sound perceptible portion of the microphone is fixed to the sound absorbing hole to be opposed thereto in this manner.
However, in the apparatuses used outdoors such as the radio receiver and a transceiver, the following problems occur.
More specifically, a speaker must put one""s mouth close to the sound absorbing hole and utter a loud voice. Moreover, since a strong current of air occurs along the front surface of the panel under the strong wind, a space, which is formed between the absorbing hole of the panel and the sound perceptible portion, functions as a column of air or a sound box and a so-called xe2x80x9cwind noisexe2x80x9d is inputted into the microphone, and this makes it difficult for a receiver side to hear the transmitting sound.
Furthermore, a linear sound guide channel is formed between the absorbing hole of the panel and the sound perceptible portion. Accordingly, when the speaker puts one""s mouth close to the sound absorbing hole as mentioned above, a strong sound pressure caused by breath directly acts on the sound perceptible portion even in an unvoiced state and a breath sound is voice-outputted, thereby grating on a receiver""s ear.
As measures against these problems, the following systems are adopted:
(1) A system in which a portion close to the sound absorbing hole of the panel surface is louvered and the current of air is scattered to prevent occurrence of resonance;
(2) A system in which a sponge or like is interposed between the sound absorbing hole and the sound perceptible portion to eliminate an element such as a column of air or the sound box in order to prevent the sound pressure caused by breath from being directly applied to the sound perceptible portion; and
(3) The size of the sound absorbing hole is formed as small as possible, and the sound guide channel is bent at the right angle twice to be guided to the sound perceptible portion of the microphone.
However, since various resonant conditions and sound pressure propagation conditions may be established depending on the state of the sound pressure caused by the uttered sound close to the panel surface and the direction of the wind, univocal louver formation as adopted in measures (1) cannot solve the aforementioned problems. In addition, it is almost impossible to form an ideal louver.
Measures (2) are substantially useful for the wind noise, breath sound and the like. However, this reduces sensitivity as a sound absorbing system and particularly attenuates high frequency components of voice frequency considerably, thereby deteriorating the reception quality on the receiver side.
Measures (3) are useful for the breath sound since the reduction in the sound absorbing hole lowers the sound absorbing efficiency. However, there is no effect on the wind noise since the sound guide channel functions as an element of the column of air.
In the radio apparatus used outdoors, conditions such as the state of noise, direction of the wind, wind force, and the like are frequently changed, and a microphone use environment is variously considered. It is naturally desired that high-quality transmission system be always maintained in any condition.
In addition, the voices represent a great variety of prosodic features based on kinds of languages such English, French, and so on and individual differences in pronunciation characteristics. There has been experimentally known a problem in which the transmission system does not match a voice with a specific prosodic feature and particularly consonants, which belong to the high frequency, become unclear. Microphone apparatuses that are adaptable to such individual circumstances are most desirable.
The aforementioned problems and demands are not limited to the radio apparatuses, and the same can be applied to the portable recording apparatuses.
In consideration of the aforementioned problems, it is an object of the present invention to provide a microphone apparatus, which can easily adjust a transmission system from a panel front surface side in response to circumstances, whereby making it possible to input a high quality voice having neither wind noise nor a breath sound generated and to implement the input of clear voice against various kinds of prosodic features of the voice.
In accordance with an embodiment of the present invention, an adjusting mechanism for use with a microphone apparatus or sound guide system having a housing with a sound guide channel for guiding a wave form between a sound absorbing hole formed in the housing to a perceptible portion of a microphone is described herein. Such adjustment mechanism is in the form of a sound box having a peripheral wall surface and adjoining first and second surfaces having respective apertures in communication with the sound absorbing hole and perceptible portion. The sound box is positioned in the sound guide channel and includes a movable piece that is slidably engaged with at least one of the surfaces and operable to move within the interior of the sound box so as to interfere with the sound guide channel upon movement of an accessible portion of an actuator coupled to the movable piece.
In a particular aspect of the present invention, the movable piece is a plate coupled to a threaded pin and disc which, when rotated, moves the plate in a linear fashion between the opposing first and second surfaces and alters the volume of the sound box.
In a second embodiment of the invention, the movable piece is substantially disc shaped and rotates around the rim of the peripheral wall surface to alter the path between the sound absorbing hole and perceptible portion of the microphone without altering the volume of the sound box.
In another aspect of the present invention, the actuator may move the movable piece incrementally within the interior of the sound box.
Yet another aspect of the present invention includes the incorporation of a movable piece with a height or cross section that is less than the height or cross section of the sound box.
In accordance with these and other aspects of the invention, the sound box may function as a variable sound filter. In one particular embodiment, the resonant frequency of the adjustable microphone apparatus for guiding sound wave forms between a sound absorbing hole and a sound perceptible portion is changed by the rotational operation of the actuator, whereby making it possible to adjust the variable sound filter to prevent wind noise and breathing sounds and the like from being input to the microphone. Additionally, the adjustment of the variable sound filter can structure the optimal sound input system which is adaptable to even various kinds of prosodic features of the voice.
In the second embodiment, such variable sound filter acts similarly. However, the resonant frequency of the sound guide system is changed when the movable piece is rotated in the sound box. Thus, the shape of the ventilation channel formed between the respective sound absorbing and sound perceptible holes is changed by the angle of rotation of the movable piece. As a result, the resonant frequency of the entirety of the adjustable microphone apparatus is changed, so as to obtain the similar effect.
Other features and aspects of the present invention will become apparent with further reference to the following drawings and specification.